This invention is concerned with polymeric conductors, and more particularly, with flexible, film-forming, organic polymeric conductors.
A great amount of research has been undertaken in an attempt to develop an organic material or class of materials which is a good conductor of electricity, yet which also is flexible, easily processable and has superior mechanical properties. Such a material would be extremely useful, for example, in fabricating semiconductors, electronic devices, and electromagnetic sensors.
There are a large number of resinous compositions which are electroconductive, usually existing as a mixture of organic resin matrix having a number of conductive particles (metals, graphite) dispersed within. These mixtures however, suffer from poor mechanical properties, primarily due to the lack of chemical bonding between the various elements.
One particular organic compound whose salts and complexed display superior conductive properties is the organic acceptor, tetracyanoquinodimethane (TCNQ): ##STR1##
It is known that TCNQ is a strong .pi.-acid which forms stable, crystalline anion-radical salts of the type M.sup.n+ (TCNQ .sub.n as well as complex salts of the formula M.sup.n+ (TCNQ ).sub.n (TCNQ.degree.), which also contain formally neutral TCNQ. These metal salts are semiconductors, existing in a rigid crystalline lattice structure.
Most semiconductors, including these TCNQ based salts, are non-flexible, opaque solids which fracture easily. Although flexible, film-forming polymeric semiconductors have been experimented with, several problems have proven difficult to solve. For example, the insulating gap between conductor particles has created a resistance that can result in thermal breakdown, and environmental damage has also proven to be a severe problem.
A recent attempt to develop materials that overcome such defects is disclosed in Ser. No. 117,162, filed 1/31/80, wherein crown ether complexes of TCNQ salts have been incorporated into various polymeric matrices to form flexible thermoplastic films. However, these compositions suffer from a resulting phase separation with the crown ethers, leading to a non-homogenous crystalline structure, with a resultant loss of efficiency. Furthermore, these compositions are also moisture sensitive under certain conditions.